Update UT - use new ErrorCohort() to mock data

[tongyu-microsoft]

This PR updates the way we mock errorCohort data.

Description

We use new ErrorCohort(new Cohort(...)) to mock cohort data, instead of mock cohort data by listing out all cohort properties. In this way, we can avoid the build error (Ke will add a rule to check on build errors in test files)

Checklist

• I have added screenshots above for all UI changes.
• I have added e2e tests for all UI changes.
• Documentation was updated if it was needed.

[codecov-commenter]

Codecov Report

Merging #1711 (321e283) into main (352c30c) will decrease coverage by 3.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1711      +/-   ##
==========================================
- Coverage   92.09%   89.00%   -3.09%     
==========================================
  Files          86      105      +19     
  Lines        4263     5577    +1314     
==========================================
+ Hits         3926     4964    +1038     
- Misses        337      613     +276     

Flag	Coverage Δ
unittests	89.00% <ø> (-3.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
raiwidgets/raiwidgets/responsibleai_dashboard.py	62.50% <0.00%> (ø)
raiwidgets/raiwidgets/error_analysis_constants.py	100.00% <0.00%> (ø)
...idgets/raiwidgets/responsibleai_dashboard_input.py	91.33% <0.00%> (ø)
raiwidgets/raiwidgets/__version__.py	100.00% <0.00%> (ø)
raiwidgets/raiwidgets/explanation_constants.py	100.00% <0.00%> (ø)
raiwidgets/raiwidgets/explanation_dashboard.py	83.33% <0.00%> (ø)
raiwidgets/raiwidgets/constants.py	99.40% <0.00%> (ø)
...dgets/raiwidgets/error_analysis_dashboard_input.py	66.09% <0.00%> (ø)
...iwidgets/raiwidgets/model_performance_dashboard.py	50.00% <0.00%> (ø)
...iwidgets/raiwidgets/explanation_dashboard_input.py	59.85% <0.00%> (ø)
... and 9 more

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[github-actions]

https://responsibleai.blob.core.windows.net/pullrequest/microsoft/responsible-ai-toolbox/tongy/updateTestCase/dashboard/index.html